It is often the case that portions of a transmitted or recorded digital data signal cannot be recovered due to problems encountered during the transmission, reception or reproduction of the digital data signal For example, in the case of magnetically recorded data, digital data that is recorded on a storage disk of a disk drive unit in some cases cannot be reproduced due to problems encountered during the recording process, defects in the storage disk, or malfunctions in the circuitry of the disk drive unit. The loss of portions of a digital data signal is particularly critical in cases where the digital data signal represents a compressed data set of a larger original data set.
Data compression is utilized in many applications where the original data set contains redundant information. It is desirable to reduce the amount of redundant information prior to storing the data, for example, in order to reduce the amount of memory capacity required to store the data. Data compression is commonly used in electronic imaging systems to reduce the amount of memory or storage space required to store digital image data. Electronic imaging systems generally capture an image as a plurality of data points or image pixels. Many images, however, have large sections, such as a blue sky or green grass, that contain identical image information. In such cases, image compression algorithms are utilized to select representative image pixels for the entire image section. Decompression algorithms can then reproduce the entire image section from the representative image pixels. Thus, the amount of memory space required to store a representation of the image can be reduced, as only the representative image pixels need to be stored.
While the above-described data compression provides the advantage of reducing the amount of memory space required, the implementation of data compression techniques requires that the data reproduction process perform with a high degree of reliability in reproducing the compressed data, as each bit of compressed data actually represents a number of original data points. For example, while the loss of number of individual image pixels would not result in a serious degradation of a reproduced image, the loss of the representative image pixels would result in serious image degradation as whole blocks or segments of the image could not be successfully reproduced. Accordingly, error correction must be provided to correct errors that occur during the reproduction process.
The concept of providing error correction to correct errors that occur during the reproduction of a recorded data signal is of course well known. U.S. Pat. No. 4,691,253 issued to Silver on Sep. 1, 1987, for example, discloses an electronic imaging camera for recording either moving or still images which incorporates a digital processing circuit that provides error correction to correct drop outs, noise spikes, etc., that may result during the reproduction of data from a flawed magnetic storage medium. Performing complex error correction routines for highly corrupted recordings can be time consuming, however, resulting in a degradation of the throughput efficiency of the imaging system as a whole. Less sophisticated methods of error correction can be utilized only with a corresponding tradeoff in image quality. Thus, the selection of an appropriate error correction routine has conventionally been a tradeoff between providing acceptable image quality with a reasonable throughput efficiency over a wide range of data reproduction conditions.
In view of the above, it would be desirable to provide a method and apparatus for performing error correction that could minimize overall system throughput time without a resulting loss in quality of the reproduced data. It is therefore an object of the invention to provide a method and apparatus for performing error correction that selects an optimum error correction routine that is to be applied to a digital data signal based on a detected characteristic of the digital data signal.